MOSCOW, Aug 19 (Reuters) - Russia is to step up safety at its nuclear facilities after wildfires threatened to engulf one centre, raising fears of a radiation leak, the head of the state nuclear corporation said on Thursday.

The fires, during Russia's worst heatwave, ringed the Soviet-built nuclear centre in Sarov, 350 km (220 miles) east of Moscow, earlier this month.

The head of state nuclear corporation Rosatom, Sergei Kiriyenko, told Prime Minister Vladimir Putin on Thursday his agency would improve fire safety.

"We agreed with (Emergencies Minister) Sergei Shoigu to install special robotic equipment to monitor and control systems at our key facilities," Kiriyenko said, according to a transcript on official site www.government.ru.

"We will also try to install the LIDAR systems on some of our key facilities," he said. "It should track any source of fire within 15 km, as well as any changes."

LIDAR, or Light Detection and Ranging, is an optical remote sensing technology that measures properties of scattered light to find the distance to an object.

Shoigu told a news conference in Moscow the cost of extinguishing fires across Russia, as well as funds allocated to building new houses, had reached 12 billion roubles ($394.2 million).

The heatwave and wildfires are estimated to shave $14 billion off this year's gross domestic product.

Kiriyenko told Putin the main challenge at facilities like the Sarov centre -- where the Soviet Union designed its first atomic and hydrogen bombs -- was that they were often located deep in forests to ensure secrecy.

During the peak of the fires in early August, Rosatom temporarily moved its nuclear materials to a safe place.

Ecologists had warned that large quantities of radioactive dust could be released into the atmosphere if forests caught fire in the Bryansk, Kaluga and Lipetsk regions, contaminated by the 1986 Chernobyl disaster.

On Tuesday, the Emergencies Ministry invited activists from campaign group Greenpeace to forests in the Bryansk region where they conducted tests they said showed normal levels of radiation, state-run RIA news agency reported. (Editing by Janet Lawrence)